valve lash adjustment for 420

[redflash]

HF recommends 004 for intake, and 006 for exhaust...on a 420, .some of you fellers suggest .003 for both. I can see that for the intake ( possibly), but when the mfger says 006 for the exhaust, it seems that your .003 will be too tight after this beast heats up......what say you, please.....little sensible direction.....

Da flash

 

[Denny]

Aluminum when it expands from heat it will also get taller. Aluminum also expands more than steel. You could also use the factory settings if you feel more comfortable.

 

[madprofessor]

However you set the lash, record your setting when cold. Then pop the valve cover immediately after a ride, check the lash while it's still good and hot. Compare the 2, make a decision.

 

[redflash]

I split the difference...used .003 instead of .004 on the intake..................and .005 instead of .006 on the exhaust. New champion rockers and new chromoly cut to length push rods......and new NR Racing twister 250 cam.......The cam has the identical lift to the stock cam, but significantly longer duration.......peak power 2000 to 5000 rpm........( motor will stay under 5000 for safety sake.......sake that's a Japanese liquor..hardy har !

Da Flash

 

[redflash]

Good idea, Mad.....will do
Thanks
Da flash

 

[panchothedog]

Hey Flash how do you like that twister 250 cam. I am thinking about getting that for my 301. It will have the internals replaced, governor removed, 50 lb
springs pipe and cold air intake with larger jet. I know it's not much more than stock lift but supposedly has a lot of duration. Think it would pull good up into the 5's. I am looking to get 5800 to 6000 rpm. It is quite a bit less expensive than the other big block cams but I am wondering if it's quite a bit less performance wise and you are the first person I have heard of running one.
Your thoughts please.

 

[redflash]

I haven't fired it yet, just installed yesterday. I'll let you know when I do.

Da Flash

 

[redflash]

Pancho, and others...ran the arachnid today WITH THE NEW 250 TWISTER CAM on the 420 powered arachnid. Yes, noticeable power increase, not as much as a 308 cam, pretty much like a mod 2 cam. spooled up a little quicker and picked up about 4-5 mph at top end.
I'll check the rpm difference tomorrow day and let you know. Every bit worth the $70.00 it cost from NR Racing.

Da Flash

 

[panchothedog]

Thank you for the feedback. Certainly sounds like you like it. I do believe that I am convinced. Don't really want to build this one full tilt. I have two of the smaller 212 cc engines done about all the way up, and while they run DAM good they are a little bit finicky. Very loud even with a muffler, harder to start, not so much in pulling but usually more pulls, and plenty of blow by enough that a catch can system is necessary. I think that's just the way it is with a high
RPM splash system oilling engine. I see the guys that oval race karts all run
catch cans. Anyway I don't all that with this one as it will as much for the adults as the grandkids. Torque and lower speed power as compared to balls
to the walls speed and maximum RPM.